1. Field of the Invention
The invention relates to a valve assembly, more particularly to a valve assembly including a valve body defining a shoulder, a stem formed with a flange, and an elastomeric O-ring sandwiched between and abutting sealingly against the flange and the shoulder through pressing action of a pressing unit.
2. Description of the Related Art
U.S. Pat. No. 4,558,874 discloses a conventional valve assembly (see FIG. 1) including: a valve body 81 formed with a stem-mounting hole and defining a fluid passage in fluid communication with the stem-mounting hole; a ball member 82 disposed movably in the valve body 81 and formed with a through-hole that is in fluid communication with the fluid passage when the ball member 82 is disposed at an opened position and that is not in fluid communication with the fluid passage when the ball member 82 is disposed at a closed position; an annular stem surrounding wall 83 fitted securely in the stem-mounting hole and formed with an inner flange 831; a stem bracket 84 secured to the stem surrounding wall 83; a stem 85 engaging threadedly the stem bracket 84, extending in an axial direction into and through the stem surrounding wall 83 to connect with the ball member 82 so as to drive rotation of the ball member 82 between the opened and closed positions, and formed with an outer flange 851 that is aligned with the inner flange 831 in the axial direction; an annular gland 86 having a portion disposed coaxially between the stem 85 and the stem surrounding wall 83; a support ring 861 disposed coaxially between the stem 85 and the stem surrounding wall 83 and abutting against the gland 86; an auxiliary packing member 87 sandwiched between and abutting against the inner and outer flanges 831, 851; and a main packing member 88 sandwiched between and abutting against the support ring 861 and the inner flange 831. The main packing member 88 includes first and second packing elements 881, 882 respectively having inclined first and second slippage surfaces that are in slipping engagement with each other. A pressing member 89 engages threadedly the stem 85 to press against a spring washer 891, which, in turn, presses against the gland 86 and the support ring 861, thereby providing an axial force acting on the main packing member 88 such that the first and second packing elements 881, 882 are compressed and expand radially to abut sealingly against the stem 85 and the stem surrounding wall 83.
Although the aforesaid conventional valve assembly can provide effective sealing, it has a relatively complex configuration and the rotational friction between the stem 85 and the main packing member 88 is still relatively large, which results in a relatively high wearing rate for the main packing member 88 and thus a decrease in the service life of the valve assembly.